Mediterranean Journal of Hematology and Infectious Diseases Original Articles
Pattern of Cerebral Blood Flow Velocity Using Transcranial Doppler Ultrasonography in Children with Sickle Cell Disorder in Lagos State, Nigeria Motunrayo Oluwabukola Adekunle, Adeola Barakat Animasahun, Ijeoma Nnenna Diaku-Akinwumi and Olisamedua Fidelis Njokanma Department of Paediatrics, Lagos State University Teaching Hospital, Ikeja, Lagos. Nigeria Competing interests: The authors have declared that no competing interests exist.
Abstract. Cerebrovascular accident (CVA) is a common, devastating neurological complication of sickle cell disorder (SCD) with a high recurrent and mortality rate. The Stroke Prevention Trial in Sickle Cell Anaemia study (STOP) recommends routine screening with transcranial Doppler ultrasonography in children aged two to sixteen years with SCD. The present study assessed cerebral blood flow velocities of children with SCD in accordance with the recommendation of routine screening by the STOP study. Methods: Transcranial Doppler ultrasonography was done for children with SCD that attended Sickle Cell Foundation, Nigeria between July and November 2015. Results: In all, 388 subjects were screened within the study period (360 HbSS and 28 HbSC). The prevalence of abnormal Time-Averaged Maximum Mean Velocity (TAMMV) of at least 200cm/second was 10.8%: this was seen solely in HbSS subjects. The mean Time-averaged mean of the maximum (TAMM) velocity were 163±25cm/sec, 162±30cm/sec and 150±30cm/sec for children less than five years, five to ten years and eleven to sixteen years respectively. Conclusion: The prevalence of abnormal TAMM velocity in children with HbSS is 10.8%. Identification of subjects at risk helped in primary CVA prevention by prompt therapy institution. Keywords: Transcranial Doppler Ultrasonography, Cerebrovascular Accident, Sickle Cell Disorder, Time-Averaged Maximum Mean Velocity. Citation:. Adekunle M.O., Animasahun A.B., Diaku-Akinwumi I.N., Njokanma O.F. Pattern of cerebral blood flow velocity using transcranial doppler ultrasonography in children with sickle cell disorder in Lagos state, Nigeria. Mediterr J Hematol Infect Dis 2017, 9(1): e2017050, DOI: http://dx.doi.org/10.4084/MJHID.2017.050 Published: August 14, 2017
Received: March 23, 2017
Accepted: July 3, 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by-nc/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Correspondence to: Motunrayo Oluwabukola Adekunle. 1-5 Oba Akinjobi Lane, Ikeja, Lagos, Nogeria. Tel: +2348036000219. E-mail: [email protected]
Introduction. Sickle cell disorder (SCD) is one of the commonest genetic diseases in the world. 1 Of the world’s population, 5.2% carry a significant variant of sickle cell gene of which over 70% occur in sub-Saharan Africa.2 Nigeria has the largest burden of sickle cell disorder in Africa with a prevalence of 3% in newborns.2 Cerebrovascular accident (CVA) is one of the most devastating complications of SCD that
causes high morbidity and mortality in children; approximately 11% of children with SCD have a CVA before the age of twenty years3 with a recurrence rate as high as 85% with the first three years of the first episode.4 The reported prevalence of CVA in children with SCD in Nigeria varied between 4.3% and 6.8%,5–7 the recurrence rate was as high as 61.5% in one of the studies.6
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Children at risk of CVA can be identified using transcranial Doppler ultrasonography which enables evaluation of cerebral artery blood flow velocity with a sensitivity of ninety percent and specificity of one hundred percent when compared with cerebral angiography.8 The Stroke Prevention Trial in Sickle Cell Anaemia study (STOP) recommends that yearly TCD screening should be done for children with SCD between the ages of two years and sixteen years with a repeat within three months for those children with abnormal results.9 Following identified risk for a cerebrovascular accident in the anterior cerebral vessels in the extended STOP trial study,10 the vessels were insonated. Early identification of children at risk of CVA with cerebral blood flow velocity of at least 200cm/second and prompt interventions help to curtail the devastating neurological complication.8 Few studies have reported the prevalence of abnormal cerebral blood flow velocities in children in Nigeria. Lagunju et al.11,12 in Ibadan, Nigeria in two studies reported 4.7% and 8.4% results of high risk for a CVA, 22.1% of the subjects had a conditional risk for a CVA. Oniyangi et al.13 at Abuja, Nigeria reported that 6.9% of subjects had abnormal cerebral blood flow velocity and 81.4% had a normal study. The present study aimed to determine the pattern of cerebral blood flow velocities of children with SCD that presents at Sickle Cell Foundation Centre, Nigeria within the studied period. Materials and Methods. It was a cross-sectional study carried out at the Sickle Cell Foundation Centre, Idi -Araba Lagos between July and November 2015. It is a non-governmental organization that receives people with SCD all over the country. The foundation offers facilities like transcranial Doppler ultrasonography, genetic counseling, major diagnostic and research facilities and prenatal diagnosis of sickle cell disorder. The study population comprised children with sickle cell disorder aged two to sixteen years in a steady state that presented to Sickle Cell Foundation Centre. Steady state was defined as the absence of any crisis for at least four consecutive weeks with no history of blood transfusion in the previous four months prior to the screening. Children with previous CVA and on hydroxyurea were excluded from the study.
In all, 388 subjects were recruited with sample size calculation based on the previously reported prevalence of 8.4% by Lagunju et al.11 Total sample size was divided into three age strata.130 subjects for the age group of less than five years, and 129 subjects each for the age group of five to ten years and eleven to sixteen years. Approval for the present study was obtained from the Health Research Ethics Committee of Lagos State University Teaching Hospital. The study was done using a Compumedics DWL Doppler machine (FDA K051 085) which is non-imaging. Recruited subjects TCD evaluations were done by one of the authors (M.O.) who had learned transcranial Doppler ultrasonography previously at the study center by a qualified trainer that does the transcranial Doppler ultrasonography at the center. All recruited subjects had the Cerebral Blood Flow Velocities measured using a 2-MHz hand held probe attached to a Doppler box according to the Stroke Prevention in Sickle Cell Disease protocol.9 The velocities of blood flow in the middle cerebral artery, internal carotid artery and anterior cerebral arteries were measured. The highest velocity in each artery was recorded as the Time-Averaged Maximum Mean Velocity (TAMMV). TAMMV less than 170 cm/second was considered normal, values greater or equal 170centimtre per second but less than 200 cm/second were conditional risks and velocity at least 200 cm/ second was considered abnormal. Further classification as low and high Conditional Risk according to TAMMV of 170 to 184cm/second and 185 to 199cm/second respectively was done.9 Results. Out of 388 subjects that had transcranial Doppler ultrasonography done, 360 were HbSS (92.8%), and 28 (7.2%) were HbSC. Their age range is two and sixteen years respectively while the mean age was 7.66±4.2 years. The female to male ratio is 1:1.4. The minimum and maximum cerebral velocities were recorded in the left anterior cerebral velocity and right middle cerebral velocity respectively as shown in table 1. The mean total TAMMV was highest in subjects below five years and lowest in subjects above ten years with a value of 161±26 and 149±31cm/sec respectively. Amongst the HbSS
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Table 1.
Table 2. Mean Time-Average Maximum Mean Velocity according to age groups. Genotype
Total (Mean±SD)
T
p-value
HbSS (Mean±SD)
HbSC (Mean±SD)
Pattern of Cerebral Blood Flow Velocity Using Transcranial Doppler Ultrasonography in Children with Sickle Cell Disorder in Lagos State, Nigeria Motunrayo Oluwabukola Adekunle, Adeola Barakat Animasahun, Ijeoma Nnenna Diaku-Akinwumi and Olisamedua Fidelis Njokanma Department of Paediatrics, Lagos State University Teaching Hospital, Ikeja, Lagos. Nigeria Competing interests: The authors have declared that no competing interests exist.
Abstract. Cerebrovascular accident (CVA) is a common, devastating neurological complication of sickle cell disorder (SCD) with a high recurrent and mortality rate. The Stroke Prevention Trial in Sickle Cell Anaemia study (STOP) recommends routine screening with transcranial Doppler ultrasonography in children aged two to sixteen years with SCD. The present study assessed cerebral blood flow velocities of children with SCD in accordance with the recommendation of routine screening by the STOP study. Methods: Transcranial Doppler ultrasonography was done for children with SCD that attended Sickle Cell Foundation, Nigeria between July and November 2015. Results: In all, 388 subjects were screened within the study period (360 HbSS and 28 HbSC). The prevalence of abnormal Time-Averaged Maximum Mean Velocity (TAMMV) of at least 200cm/second was 10.8%: this was seen solely in HbSS subjects. The mean Time-averaged mean of the maximum (TAMM) velocity were 163±25cm/sec, 162±30cm/sec and 150±30cm/sec for children less than five years, five to ten years and eleven to sixteen years respectively. Conclusion: The prevalence of abnormal TAMM velocity in children with HbSS is 10.8%. Identification of subjects at risk helped in primary CVA prevention by prompt therapy institution. Keywords: Transcranial Doppler Ultrasonography, Cerebrovascular Accident, Sickle Cell Disorder, Time-Averaged Maximum Mean Velocity. Citation:. Adekunle M.O., Animasahun A.B., Diaku-Akinwumi I.N., Njokanma O.F. Pattern of cerebral blood flow velocity using transcranial doppler ultrasonography in children with sickle cell disorder in Lagos state, Nigeria. Mediterr J Hematol Infect Dis 2017, 9(1): e2017050, DOI: http://dx.doi.org/10.4084/MJHID.2017.050 Published: August 14, 2017
Received: March 23, 2017
Accepted: July 3, 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by-nc/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Correspondence to: Motunrayo Oluwabukola Adekunle. 1-5 Oba Akinjobi Lane, Ikeja, Lagos, Nogeria. Tel: +2348036000219. E-mail: [email protected]
Introduction. Sickle cell disorder (SCD) is one of the commonest genetic diseases in the world. 1 Of the world’s population, 5.2% carry a significant variant of sickle cell gene of which over 70% occur in sub-Saharan Africa.2 Nigeria has the largest burden of sickle cell disorder in Africa with a prevalence of 3% in newborns.2 Cerebrovascular accident (CVA) is one of the most devastating complications of SCD that
causes high morbidity and mortality in children; approximately 11% of children with SCD have a CVA before the age of twenty years3 with a recurrence rate as high as 85% with the first three years of the first episode.4 The reported prevalence of CVA in children with SCD in Nigeria varied between 4.3% and 6.8%,5–7 the recurrence rate was as high as 61.5% in one of the studies.6
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Children at risk of CVA can be identified using transcranial Doppler ultrasonography which enables evaluation of cerebral artery blood flow velocity with a sensitivity of ninety percent and specificity of one hundred percent when compared with cerebral angiography.8 The Stroke Prevention Trial in Sickle Cell Anaemia study (STOP) recommends that yearly TCD screening should be done for children with SCD between the ages of two years and sixteen years with a repeat within three months for those children with abnormal results.9 Following identified risk for a cerebrovascular accident in the anterior cerebral vessels in the extended STOP trial study,10 the vessels were insonated. Early identification of children at risk of CVA with cerebral blood flow velocity of at least 200cm/second and prompt interventions help to curtail the devastating neurological complication.8 Few studies have reported the prevalence of abnormal cerebral blood flow velocities in children in Nigeria. Lagunju et al.11,12 in Ibadan, Nigeria in two studies reported 4.7% and 8.4% results of high risk for a CVA, 22.1% of the subjects had a conditional risk for a CVA. Oniyangi et al.13 at Abuja, Nigeria reported that 6.9% of subjects had abnormal cerebral blood flow velocity and 81.4% had a normal study. The present study aimed to determine the pattern of cerebral blood flow velocities of children with SCD that presents at Sickle Cell Foundation Centre, Nigeria within the studied period. Materials and Methods. It was a cross-sectional study carried out at the Sickle Cell Foundation Centre, Idi -Araba Lagos between July and November 2015. It is a non-governmental organization that receives people with SCD all over the country. The foundation offers facilities like transcranial Doppler ultrasonography, genetic counseling, major diagnostic and research facilities and prenatal diagnosis of sickle cell disorder. The study population comprised children with sickle cell disorder aged two to sixteen years in a steady state that presented to Sickle Cell Foundation Centre. Steady state was defined as the absence of any crisis for at least four consecutive weeks with no history of blood transfusion in the previous four months prior to the screening. Children with previous CVA and on hydroxyurea were excluded from the study.
In all, 388 subjects were recruited with sample size calculation based on the previously reported prevalence of 8.4% by Lagunju et al.11 Total sample size was divided into three age strata.130 subjects for the age group of less than five years, and 129 subjects each for the age group of five to ten years and eleven to sixteen years. Approval for the present study was obtained from the Health Research Ethics Committee of Lagos State University Teaching Hospital. The study was done using a Compumedics DWL Doppler machine (FDA K051 085) which is non-imaging. Recruited subjects TCD evaluations were done by one of the authors (M.O.) who had learned transcranial Doppler ultrasonography previously at the study center by a qualified trainer that does the transcranial Doppler ultrasonography at the center. All recruited subjects had the Cerebral Blood Flow Velocities measured using a 2-MHz hand held probe attached to a Doppler box according to the Stroke Prevention in Sickle Cell Disease protocol.9 The velocities of blood flow in the middle cerebral artery, internal carotid artery and anterior cerebral arteries were measured. The highest velocity in each artery was recorded as the Time-Averaged Maximum Mean Velocity (TAMMV). TAMMV less than 170 cm/second was considered normal, values greater or equal 170centimtre per second but less than 200 cm/second were conditional risks and velocity at least 200 cm/ second was considered abnormal. Further classification as low and high Conditional Risk according to TAMMV of 170 to 184cm/second and 185 to 199cm/second respectively was done.9 Results. Out of 388 subjects that had transcranial Doppler ultrasonography done, 360 were HbSS (92.8%), and 28 (7.2%) were HbSC. Their age range is two and sixteen years respectively while the mean age was 7.66±4.2 years. The female to male ratio is 1:1.4. The minimum and maximum cerebral velocities were recorded in the left anterior cerebral velocity and right middle cerebral velocity respectively as shown in table 1. The mean total TAMMV was highest in subjects below five years and lowest in subjects above ten years with a value of 161±26 and 149±31cm/sec respectively. Amongst the HbSS
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Table 1.
Table 2. Mean Time-Average Maximum Mean Velocity according to age groups. Genotype
Total (Mean±SD)
T
p-value
HbSS (Mean±SD)
HbSC (Mean±SD)
